1. Field of the Invention
This invention relates to a photographic, especially an electrophotographic, copying machine of the through-slit exposure type, and more particularly to a simplified photographic copying machine of such type for use with originals in the form of sheet (hereinafter referred to as "sheet originals") and .[.and.]. originals in the form of book or the like (hereinafter referred to as "thick originals").
2. Description of the Prior Art
While a copying machine exclusively for use with sheet originals cannot copy thick originals such as books or the like, it can copy sheet originals simply by placing such originals in a feed port and does not involve the backward or return stroke of its original supporting carriage or its optical system. Therefore, such copying machine can increase the copying speed and is simple to construct and inexpensive to manufacture.
On the other hand, a copying machine for use with books or other thick originals is characterized by its capability of copying sheet originals as well as thick originals, but the machine of this type involves the procedures of opening an original setting cover, placing a sheet original or a thick original on an original supporting glass sheet, closing the cover and depressing a copy button. Further, the return stroke of its original carriage or its optical system is involved not only to limit the copying speed but also to complicate the machine construction and accordingly increase the cost of the machine.
For these reasons, the copying machines of the foregoing two types have been enjoying their own unique demand.
In offices, however, it is usually the case that sheet originals are copied much more often than books or other thick originals, which are rarely required for copying. In view of such situation, a copying machine of a further type has been proposed which can copy both sheet originals and thick originals without reducing its merits as the sheet original copying machine including the simplicity of construction, a higher copying speed, low cost of the manufacture, etc. This versatile copying machine is either such that the machine parts overlying the passage surface for sheet originals are made into a detachable construction which, for a thick original to be copied, may be detached to expose the sheet original transport rollers of the machine proper, whereby the thick original such as book or the like is manually pressed against these rollers and exposed to light while being moved by the rubber rollers to produce a copy, or such that a carrier formed of transparent glass or plastics sheet is provided to support a book or the like thereon and two or more pairs of transport rollers are provided to hold therebetween the ends of the carrier so as to move the carrier for accomplishing exposure. Such machine is characterized by its relatively low cost of the manufacture, but suffers from various demerits and practical problems as enumerated hereunder.
1. The procedure of detaching some of the machine parts is unavoidably involved.
2. Possible variations in the manual pressure imparted to the book or the like for keeping it against the driven rubber rollers and corresponding variations occurring in the speed at which the book or the like is manually moved along the rubber rollers may cause great variations in load to the drive of the machine proper, which in turn would result in unstability of the formed image and accordingly a seriously reduced quality of the resultant copy.
3. The detection of the leading edge of the original effected by a detection switch is subject to errors which would cause a great degree of irregularity in the location of the leading edge of the resultant copy image, because when opened for copying, the leading edge of the thick original such as book or the like (as viewed in the direction of the original feeding) provides a complicated configuration (due to the presence of its cover or to the inclined edge surface of the book formed when it is opened).
4. The roller driving gear or sprocket wheel located at one end of the original transport rollers is unavoidably projected upwardly beyond the plane of the original passage surface to prohibit flat formation of the original passage surface and accordingly prevent a part of a bulky original from being duly copied.
Also, in the type of machine which is provided with a carrier, cumbersome procedures are involved in the maintenance of the carrier, in addition to the troublesome procedures of mounting and dismounting the same carrier.